Commentary

Cleaning up Clostridium difficile infection

Bacterial spores are frequently intrinsically resistant to biocides and only a number of alkylating and oxidising biocides are sporicidal under certain conditions. Activity against spores is affected by several key factors such as concentration, exposure time, soiling, and the types of surface to be treated. Sporicidal efficacy is usually achieved after an exposure time of several minutes with a high concentration of a biocide. Failure to understand these factors will result in decreased sporicide activity and spore survival. Sporicides in healthcare settings are used for surface disinfection and for the high level disinfection of certain medical devices (e.g. endoscopes). With efficacy data in mind, sporicidal activity should be achieved for the disinfection of medical devices where both high concentration and long exposure time occur. However, for the disinfection of environmental surfaces, high concentration is not recommended, nor is long exposure time achievable. In this case, sporicidal activity is severely reduced and spore survival following treatment is to be expected and contributes to the explanation of spore persistence on surfaces.

Clostridia are not normally considered to be zoonotic pathogens, although many species affect both humans and domestic animals. Three cases in which organisms occur, possibly via direct or indirect transmission, in both food animals and humans are considered here. Strains of Clostridium perfringens that produce enterotoxin (CPE) are typically transmitted to humans in contaminated, improperly handled foods. Pathogenesis is based upon action of CPE in the intestine, and disease is usually self-limiting. Infection of domestic animals by CPE-producing C. perfringens is uncommon. C. perfringens type C is best known as a pathogen of neonatal domestic animals, which acquire the infection from the dam. The course may be peracute, and prevention by vaccination of the dam is universally advocated. Humans consuming meat contaminated with type C may develop enteritis necroticans, with segmental hemorrhagic and necrotic jejunitis, which must usually be treated by bowel resection. Clostridium difficile is a pathogen of both humans and domestic animals. Examination of retail meats by bacteriologic culture has revealed genotypes of C. difficile that in many cases are identical to those from food animals and diseased humans. Transmission, food animals to foods to humans, has not been documented.

Routine surface cleaning is recommended to control the spread of pathogens in hospital environments. In Norway, ordinary cleaning of patient rooms is traditionally performed with soap and water. In this study, four floor-mopping methods – dry, spray, moist and wet mopping – were compared by two systems using adenosine triphosphate (ATP) bioluminescence (Hygiena and Biotrace). These systems assess residual organic soil on surfaces. The floor-mopping methods were also assessed by microbiological samples from the floor and air, before and after cleaning. All methods reduced organic material on the floors but wet and moist mopping seemed to be the most effective (P < 0.001, P < 0.011, respectively, ATP Hygiena). The two ATP methods were easy to use, although each had their own reading scales. Cleaning reduced organic material to 5–36% of the level present before cleaning, depending upon mopping method. All four mopping methods reduced bacteria on the floor from about 60–100 to 30–60 colony-forming units (cfu)/20 cm² floor. Wet, moist and dry mopping seemed to be more effective in reducing bacteria on the floor, than the spray mopping (P = 0.007, P = 0.002 and P = 0.011, respectively). The burden of bacteria in air increased for all methods just after mopping. The overall best cleaning methods seemed to be moist and wet mopping.

Clostridium difficile-associated diarrhoea (CDAD) presents mainly as a nosocomial infection, usually after antimicrobial therapy. Many outbreaks have been attributed to C. difficile, some due to a new hyper-virulent strain that may cause more severe disease and a worse patient outcome. As a result of CDAD, large numbers of C. difficile spores may be excreted by affected patients. Spores then survive for months in the environment; they cannot be destroyed by standard alcohol-based hand disinfection, and persist despite usual environmental cleaning agents. All these factors increase the risk of C. difficile transmission. Once CDAD is diagnosed in a patient, immediate implementation of appropriate infection control measures is mandatory in order to prevent further spread within the hospital. The quality and quantity of antibiotic prescribing should be reviewed to minimise the selective pressure for CDAD. This article provides a review of the literature that can be used for evidence-based guidelines to limit the spread of C. difficile. These include early diagnosis of CDAD, surveillance of CDAD cases, education of staff, appropriate use of isolation precautions, hand hygiene, protective clothing, environmental cleaning and cleaning of medical equipment, good antibiotic stewardship, and specific measures during outbreaks. Existing local protocols and practices for the control of C. difficile should be carefully reviewed and modified if necessary.

Hospital cleaning currently has a high media profile. The effectiveness of an existing ward-cleaning regimen was assessed at selected sites over a 14 day period and shown to be highly variable. The cleaning regimen was subsequently modified in two stages, both changes involving a rinse stage and substituting cloths with disposable paper towels. One modification continued using the existing detergent; the other replaced detergent with a quaternary ammonium sanitiser. Both modifications yielded significantly lower and more consistent bacterial counts. Assessment of residual organic soil using adenosine triphosphate (ATP) detection demonstrated that failure rates (measurements exceeding benchmark clean value of 500 relative light units (RLU)) fell from 86–100% after existing cleaning methods, to 0–14% after modified cleaning. Maximum ATP readings fell from 163 870 to 2289 RLU. Incorporating a quaternary ammonium sanitiser into the cleaning regimen produced a further slight, but not significant, improvement in cleaning efficacy. These findings suggest that simple improvements can be made to existing cleaning regimens to increase their efficacy.